Modern gas turbine engines are commonly provided with a combustor which is of generally annular configuration. Usually a wall or bulkhead is provided at the upstream end of the combustor which is suitably apertured to receive a number of fuel burners. The fuel burners are equally spaced around the bulkhead and direct fuel into the combustor to support combustion therein. The combustor bulkhead is therefore usually close to the high temperature combustion process taking place within the combustor, making it vulnerable to heat damage.
One way of protecting the bulkhead from the direct effects of the combustion process is to position heat shields on its vulnerable parts. Typically each heat shield is associated with a corresponding fuel burner, extending both radially towards the radially inner and outer extents of the bulkhead and circumferentially to abut adjacent heat shields. Each heat shield is spaced apart from the bulkhead so that a narrow space is defined between them. Cooling air is directed into this space in order to provide cooling of the heat shield and so maintain the heat shield and the bulkhead at acceptably low temperatures.
In practice, it has proved to be difficult to ensure that the majority of each of the heat shields remains at an acceptably low temperature without the use of excessive amounts of cooling air. Since the cooling air is normally air which has been compressed by the gas turbine engine's compressor, any excessive use of that air for cooling purposes is undesirable in view of the detrimental effect which this has upon overall engine efficiency.